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Downhole Chemical Scale Inhibiting Practice In Yangyi Geothermal Power Plant
The geothermal production wells of Yangyi geothermal power plant are high temperature artesian well.The 16MW Omart project adopts ZK203 and ZK208 as production Wells and ZK403 as injection well.According to different production well conditions, the dosing system injects the inhibitor below the flash point of the production well to keep the inhibitor evenly dispersed during the rise of the geothermal fluid, thus preventing the downhole calcium carbonate scaling problem caused by the separation of carbon dioxide from the geothermal water at 200-250 meters underground.Due to the high content of silicate in geothermal fluid, the solubility of silicate is positively correlated with the temperature of geothermal brine. Omat calculates and simulates the operating conditions of the system to comfirm the temperature of silicate precipitation. Before the project is put into operation, it is recommended that the temperature of injection water should controlled above 80℃ to aviod the scaling problem of silicate.After on-site production testing and observation, Yangyi finally controls the injection temperature above 60℃, and the silicate scaling in the heat exchanger and the recharge system is controllable.At the beginning of the power plant put into operation, the mechanical faults of dosing system has completely solved, the chemical inhibit system ，put into operation October 2018，run in good condition, two production Wells , steam collection system, ORC heat exchanger and injection system without scaling problem , generating system has no trip or abnormal maintenance caused by the scaling problem .The attempt of chemical scale inhibition in Yangyi 16MW project was very successful.The 16MW ORMAT project adopted imported scale inhibitor when it was put into production. Through on-site test YangYi achieved the domestic production of scale inhibitor in 2020, which reduced the cost of chemical scale inhibitor by about half. In 2023, the new domestic scale inhibitor was further tested in Yangyi Power Plant. The test results show that the new domestic scale inhibitor can ensure excellent scale inhibition effect and further reduce the cost to one-third of the cost of the original imported scale inhibitor. Domestic scale inhibitor has also been used in the development of other fields in China.